Explain Everything is a fantastic app that allows users to a virtual white board to display work and answer questions. Your explanation and work can be recorded in tandem to construct a video file. Images can be imported to help with this process. Check out the video link for a demonstration and explanation.
http://www.youtube.com/watch?v=I4JOsrEsyo0
http://www.youtube.com/watch?v=I4JOsrEsyo0
